Each sport has a different requirement for the number of players at each position required to play a game. College teams automatically meet this requirement during walk-ons, and are not allowed to do anything (cuts or player position changes) that would give them an illegal roster. Pro GMs have more freedom, but will be fined for each game that their roster has problems. Pro teams can also forfeit if the roster is sufficiently bad. The requirements are listed below:

Pro sports also have limits on the total number of players that must be on the roster, both major and minor league. If a player is injured, a team may sign an additional player for the duration of the injury, relegating the injured player to injured reserve. (Minor league teams do not have injured reserve.) The total number of players are:Baseball, Hockey: 25Basketball: 12Football: 45Soccer: 22

Failure to have the right number of players on the roster will invoke a per-game fine. The formula is rather complex, but for the sake of completeness it is given here:

A = maximum of the team's current balance, the team's financial outlook or zero.

B = the luxury tax threshold for the sport

C = the number of players you are over the limit

D = the maximum number of players on the roster

E = the number of regular season + preseason games

Fine = 0.2 * ( A + B ) * (1 + 2.25*(C-1)/D ) / E

In the simplest cases (a team with no money and not turning a profit, with only one player over the limit), the fines work out to:Baseball: $0.057 millionBasketball: $0.053 millionFootball: $0.487 millionHockey: $0.065 millionSoccer: $0.119 million